The present invention relates to valve system maintenance and manufacture and pertains particularly to a method and apparatus for reseating globe type valves.
A great many globe type valves are used in industry and commerce for controlling the flow of fluids in fluid systems. Such valves of the globe type includes a valve body having a through passage including a portion surrounded by a valve seat with a valve member normally termed a disc axially movable on a rotatable and axially movable stem into and out of a seating engagement with the valve seat to control flow of fluid through the valve. Fluids flowing through such a valve corrode, pit, and wear away the valve disc seating surface and the valve seat. This permits the valve to leak fluids by the valve and becomes wasteful and in many cases hazardous.
Such valves can frequently be reconditioned by regrinding the valve seat and the valve disc seating surface. The surfaces are then lapped to provide a close fitting seal of the mating surfaces.
Frequently only a lapping operation is needed in order to reseat the valve and its seat in order to make the valve correctly function again. Such operation in the prior art technique is generally carried out by a welding the valve disc to the valve stem to prevent relative rotation thereof. Thereafter a grinding or lapping compound is placed on the valve seat or seating surface and the rotation of the valve stem and disc is carried out until a proper mating of these surfaces is obtained. After the lapping or mating of the surfaces is obtained the valve stem and disc is then removed and the welding is ground off to permit the valve disc to rotate relative to the valve stem.
The problem with this approach is that an expert welder is needed to provide the welding and grinding facilities are needed in order to grind the weld off. Frequently such valve discs and stems are damaged beyond repair by either the welding or by the subsequent grinding of the weld from the valve and stem.
Accordingly, it is desirable that a simple quick and easy method and apparatus be available for quickly and conveniently securing valve discs against relative rotation for proper lapping of the valve seats.